Ingenol-3-angelate (PEP005, ingenol mebutate) is a diterpene-ester of the ingenol family which is isolated from various Euphorbia species, particularly from Euphorbia peplus. The compound is presently subject for clinical development for the treatment of actinic keratosis and for non-melanoma skin cancer.
Ingenol-3-acylates, mainly of long-chain saturated and unsaturated aliphatic fatty acids, have been isolated from various Euphorbia species [H. Gotta, Z. Naturforschung, (1984), 39b, 683-94; K. Abo, Fitoterapia, (1988), 244-46, S. Zayed, 1 Cancer Res. Clin. Oncol. (2001), 127, 40-47]. Furthermore, a small number ingenol-3-acylates have been prepared by semi-synthesis (B. Sorg et. al., Z. Naturforsch., (1982), 37b, 748-56). Some of these ingenol derivatives have been described and tested to be strong irritants and strong tumor-promoting agents. [B. Sorg et. al., Z. Naturforsch., (1982), 37b, 748-56; B. Sorg et. al., Carcinogenesis, (1987), 8, 1-4].
Besides the aliphatic ingenol esters also aromatic esters of ingenol are known. Milliamine C, an ingenol-3-anthraniloate derivative was described (Marston, A. Planta Medica, (1983), 47, 141-47). Also ingenol-3-benzoate has been described (Sorg, B.; Z Naturforschung, (1982), 37b, 748-56), as well as ingenol-3-(2-methylamino)benzoate (Mainieri, F.; Natural Product Communication, (2007), 2(4), 375-379).
Angelic acid and angelic acid esters, as present in ingenol-3-angelate, are prone to isomerisation of the double bond to form the tiglate ester, particularly at basic pH [Beeby, P., Tetrahedron Lett. (1977), 38, 3379-3382, Hoskins, W. M., J. Chem. Soc. Perkin Trans. 1, (1977), 538-544, Bohlmann, F. et. al., Chem. Ber. (1970), 103, 561-563]. Furthermore, ingenol-3-acylates are known to be unstable as they rearrange to afford the ingenol-5-acylates and ingenol-20-acylates [Sorg, B. et. al, Z. Naturforsch., (1982), 37B, 748-756].
WO99/08994 describes isolation of compounds from Euphorbia plant and their use in cancer and other neoplastic diseases hereunder actinic keratosis or solar keratosis. WO01/93883 describes ingenol derivatives different from the present invention for prophylaxis of a PKC-related condition or disorder in a subject. Diseases mentioned in WO01/93883 are: asthma, atherosclerosis, atopic dermatitis, autoimmune disease, bipolar disorder, blood disorder, cardiac hypertrophy, depression, diabetes, hypertension, hyperplastic dermatosis, multiple sclerosis, myocardial ischemia, osteoarthritis, psoriasis, rheumatoid arthritis, transplantation and latent virus. WO01/93884 discloses ingenol derivatives different from the present invention, and their use in treating inflammatory conditions such as resulting from pathogenic organisms, virus, yeast, fungus, worms, insects, arachnids, nematodes, aemobe etc. WO01/93885 describes ingenol derivatives different from the present invention for immunopotentiation. WO08/131,491 describes ingenol derivatives different from the present invention for HPV virus infections. WO06/063382 discloses ingenol derivatives different from the present invention for treatment of solid cancers. AU 2006201661 discloses a method for treating acute myeloid leukemia using ingenol-3-angelate. WO02/11743 describes a particular use in prostate and bladder cancer. Ingenol derivatives are described in WO07/059,584 for promoting wound healing. WO2010/091472 describes use of ingenols and derivatives in other cosmetic applications.
Ingenol-3-angelate is believed to have a dual mode of action: 1) Induction of cell death by direct cytoxicity or induction of apoptosis and 2) an immunostimulatory effect dominated by neutrophil recruitment and activation (Rosen, R. H., et al., J Am Acad Derm (2011), e-published November 2011; Ersvaer, E., et al., Toxins, (2010), 2, 174-194). Nanomolar concentrations of the agent cause activation and modulation of protein kinase C (PKC) classical and novel isoforms, with particular importance of PKCdelta. Through activation of PKCdelta the agent induces apoptosis in susceptible cells (Hampson, P., et al., Blood, (2005), 106, 1362-1368; Cozzi, S. J., et al., Cancer Res, (2006), 66, 10083-10091). Rapid cytotoxicity on cancer cells is observed at high micromolar concentrations (Ogbourne, S. M., et al., Cancer Res (2004), 64, 2833-2839). Through activation of various PKC isoforms the agent also induces pro-inflammatory effects, including release of pro-inflammatory mediators (Challacombe, J. M., et al., J Immunol (2006), 177, 8123-8132, activation of vascular endothelium (Hampson, P., et al., Cancer Immunol Immunother, (2008), 57, 1241-1251); chemoattraction of neutrophils through induction of interleukin 8 in keratinocytes and development of specific anti-cancer immune responses by CD8+ cells through adjuvant properties in animal models (Le, T. T., et al., Vacccine, (2009), 27, 3053-3062).
Compounds exerting dual mode of action by induction of cell death by direct cytoxicity or induction of apoptosis, and by an immunostimulatory effect involving neutrophil recruitment and activation, may be useful for treatment of conditions associated with hyperplasia or neoplasia. Compounds inducing cell death by primary and/or secondary necrosis and compounds exhibiting a pro-apoptotic effect may reduce unwanted cell growth and remove unwanted cells, and furthermore, stimulation of the innate immune response and adjuvant effects may augment the biological response against aberrant or transformed cells.
Compounds inducing cell death by primary and/or secondary necrosis may be useful for treatment of cosmetic conditions, as these compounds may kill or remove unwanted tissue or cells.
There is a need to find new ingenol derivatives, with a similar or improved biological activity compared to ingenol-3-angelate, exhibiting suitable stability. Furthermore, there is a need to find new ingenol derivatives which induce cell death by cytotoxicity or apoptosis and/or induce an immunostimulatory effect.
The present invention provides aromatic or carbocyclic 3-O-acyl ingenol derivatives useful for treatment of conditions associated with the use of ingenol-3-angelate or useful for conditions which are affected by induction of cell death by cytoxicity or induction of apoptosis and/or by an immunostimulatory effect.
Compounds of the present invention stimulate neutrophil oxidative burst, which is part of the innate immune response.
Compounds of the present invention stimulate keratinocyte IL-8 release, thus inducing an immunostimulatory effect.
Some compounds of the present invention induce rapid necrosis.
Compounds of the present invention exhibit suitable stability.
Some compounds of the present invention exhibit improved stability compared to ingenol-3-angelate.
Some compounds of the present invention exhibit improved activity in neutrophil oxidative burst assay compared to ingenol-3-angelate.
Some compounds of the present invention exhibit improved activity in IL-8 release assay compared to ingenol-3-angelate.
Some compounds of the present invention exhibit improved activity in necrosis assay compared to ingenol-3-angelate.